Abstract
BACKGROUND: Aging is marked by a decline in physical function. Although the biological underpinnings for this remain unclear, loss of regenerative capacity has been proposed as one cause of the loss of physical function that occurs over time. The quantity of circulating progenitor cells (CPCs) may be one reflection of regenerative capability. We sought to determine whether certain specific CPC subpopulations were associated with physical function. METHODS: Baseline CPCs were measured in 129 randomized participants in the Enhanced Fitness clinical trial based on the cell surface markers CD34, CD133, CD146, and CD14 and aldehyde dehydrogenase (ALDH) activity. Physical function was assessed using usual and rapid gait speed, 6-minute walk distance, chair stand time, and balance time. RESULTS: Low counts of early angiogenic CPCs identified as CD34(+), CD34(+)CD133(+), and ALDH-bright (ALDH(br)) cells were associated with low usual gait speed (p < .005, p < .001, and p < .007), rapid gait speed (p < .001, p < .003, and p < .001), and 6-minute walking distance (all comparisons p < .001), and longer time required to complete five chair stands (p < .006, p < .002, and p < .004). CPC counts of mature endothelial or monocytic markers were not associated with physical function. CONCLUSIONS: The numbers of CD34(+) and ALDH(br) CPCs are significantly lower in patients with impaired physical function. Further studies are needed to determine the underlying causes for this association.